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Published on January 27th, 2015 | by Derek Markham

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Smart Solar Irrigation In Senegal Offers Pay-As-You-Go Power

January 27th, 2015 by  


Originally published on Ecopreneurist.

In rural areas of Senegal, getting water for irrigating crops often comes with a hefty price tag, not only in terms of the cost to buy the fuel for it (about $1 per day for an average gas-powered irrigation pump), and the time necessary to procure it from the nearest gas station (which could be an hour away by car), but also in regards to the polluting emissions of the pumps themselves, which are not clean-burning or very efficient. Because of these barriers, quite a bit of watering is done by hand, which can often take all day to do and limit each farmer’s crop production.

DSC09339-700x393Putting in solar powered irrigation pumps might be one possible solution, but most small farmers, such as those in Senegal’s Niayes zone, where over half of the nation’s agricultural products are grown, can’t afford a gasoline pump, much less a standalone solar pump, so solar irrigation hasn’t yet been a viable option there. But thanks to the work of Columbia University’s Sustainable Engineering Lab (SEL), a different model of providing solar irrigation may prove out to be the most sustainable solution for small farmers.

The Smart Solar Irrigation project is based on building a centralized solar plant, where a single PV array and monitoring and control system provides the power to the individual pumps of its customers, who pay only for what they use with a prepaid credit program. To keep the costs affordable, the system developed by SEL is a battery-less one (a battery bank not only adds to the initial cost, but also requires future costs for replacement) that only pumps when the sun is shining.

solarIrrigationWorks

Here’s how it works:

Centralized solar & monitoring: Electricity is generated centrally by a single, solar PV array. A custom-made battery-less AC system controls and monitors pump function for 7+ farmers.

Pre-paid credit: Electricity is sold by a micro-utility to farmers using a pre-paid credit system similar to cell phone scratch card systems, only paying for what they consume.

Decentralized pumps: Farmers retain autonomy of their individual wells and pumps.

SEL just finished installing the first of three of these pilot solar irrigation systems, each of which will provide solar electricity to pump water for 7 farmers in rural Senegal, as part of a USAID Powering Agriculture grant. The first system, a 6.8kW solar array, was installed in Gabar, Senegal, with the central controller located in a small concrete building nearby, where it will serve as a micro-utility supplying electricity to local farmers.

More about the smart solar irrigation system from SEL can be found at the website.

Reprinted with permission.


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About the Author

Derek lives in southwestern New Mexico and digs bicycles, simple living, fungi, organic gardening, sustainable lifestyle design, bouldering, and permaculture. He loves fresh roasted chiles, peanut butter on everything, and buckets of coffee. Catch up with Derek on Twitter, Google+, or at his natural parenting site, Natural Papa!



  • Larmion

    The fact that irrigation is required shows that water is a limiting resource for local agriculture. You’re now introducing a system that shifts all irrigation to daytime, when evaporation losses are maximised. So you’re essentially encouraging farmers to waste water, already a scarce resource (especially in the north of Senegal).

    Oh well, maybe a battery can be added in a few years time when prices have fallen enough.

    • Bob_Wallace

      Cheaper than batteries – elevate some plastic tanks and use gravity flow before and after the Sun starts cooking.

      Pair that with some drip irrigation and things would get very efficient. In a place that’s used to hand watering moving a drip system several times a day would probably be quite acceptable.

    • MarTams

      Drip irrigation under a full canopy or under soil surface is not significantly affected by time of day. Learn how to farm.

      • Larmion

        The upfront cost of a drip system is too high for this scenario. The pictures in the links in the article clearly show what you can expect in this scenario: a rubber hose at best, trench irrigation at worst.

        And a full canopy isn’t common either. Agroforestry and other partially shaded systems are still relatively uncommon.

        • Bob_Wallace

          100′ of drip tape is about $10. Might be a lot cheaper to invest in a drip system than create a larger pumping system.

          • Larmion

            But it isn’t included in the proposal as it’s reported here, and that’s likely for a reason.

            Drip irrigation systems need proper maintenance and, if cheap tubing is used, frequent repair and replacement. It’s the little things. Things like rodents.

            I’m also not sure about the local soil composition and water source. If the water is somewhat saline and/or the soil has nearly impermeable layers (very common in Africa), drip irrigation is prone to causing salt buildup. All irrigation has this issue to some extent, but gradual low-flow methods like drip irrigation more than most.

            From what I gather, this is a project serving the poorest of the poor. Drip irrigation is quite expensive upfront relative to alternatives, especially when pumps and traditional irrigation systems are already in place as they are here.

          • Bob_Wallace

            $10 for a 100′ run. Pick it up and move it. Take it up at night so that rodents don’t eat it.

            I’ve used T-tape for many years.

            If salt build up is a problem then do a flushing with the hose from time to time.

            Drip irrigation is considerably cheaper than putting in enough pumping ability to allow wasting a lot of water. Some of us have lived the life and done the math.

    • John Humphrey

      Great discussion guys. I’ll comment on a few points:
      Adding a tank requires a plot of land to site it (none available)
      There are also cultural barriers to “sharing” water as would be implied by a tank.

      Yes irrigation is happening during the day, it already was, but now it is happening most during solar max. this is something we are aware of and paying attention to.

      Waiting for battery tech to evolve to a point where it makes sense is not going to get us anywhere. It’s not there. Someday maybe…

      as far as drip irrigation goes, for one thing, the farmers rotate crops, so it’s not that easy to move all the tubes around. Also, we are doing higher flow rates for short periods. Might make sense with an elevated tank, but not for this scenario…

  • Will E

    Solar is fit for small and big and Solar is cheap.
    how come still talking about Solar is expensive.
    it was years ago. now Solar is cheap. also in Senegal everywhere.
    ONCE AGAIN
    SOLAR IS CLEAN CHEAP AND EASY. ALLOVERTHEWORLD.
    ps I have Solar and heatpump and no energy bill for 3 years now.
    it was cheap it is clean and it was easy to install.
    it is hard to drain the petrol heads and let the sun shine in.

  • Matt

    Wonderful idea, let’s bypass fossil fuels, and provide a truly sustainable model for farmers!

  • JamesWimberley

    Senegal has five mobile payment operators (link), including one run by the giant French telco Orange. Africans are pretty familiar and comfortable with the concept.

    What I like about this project is that as much thought has obviously gone into the institutional design as the technology. Problems are not solved just with gadgets dropped from helicopters.

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